Heat sink device

ABSTRACT

A heat sink is provided. The heat sink contains a first vapor chamber section having a top surface and a bottom surface that is in thermal contact with a heat source, a second vapor chamber section that extends vertically from the top surface of the first vapor chamber section, and heat-dissipating fins that are attached to the second vapor chamber section. The first and second vapor sections are connected to each other forming a continuous vapor chamber space.

TECHNICAL FIELD

The technical field relates generally to cooling systems forelectronics, and more particularly to a heat sink with vapor chambersand thermal dissipating fins.

BACKGROUND

Increasing levels of component power and power density from electronicdevices such as integrated circuits and memory are creating an increaseddemand for thermal management solutions. For example, hid blade servershave been in great demand in recent years due to their outstandingperformance. This high density computing power, however, comes with verylimited space in the server enclosure. Accordingly, high performanceheat sinks are necessary for efficient cooling. The heat sinks in usetoday have reached their limit in dissipating the heat generated bypower chips. A need for more efficient cooling exists to expand thethermal dissipation performance envelope.

SUMMARY

A heat sink is disclosed. The heat sink comprises a first vapor chambersection having an upper surface and a lower surface, a second vaporchamber section extending vertically from said upper surface of saidfirst vapor chamber section, and heat dissipating fins extendinghorizontally from said second vapor chamber section, wherein said lowersurface is in thermal contact with a heat source and wherein said firstand second vapor sections are connected to each other, forming acontinuous vapor chamber space.

Also disclosed is a heat site comprising: a hollow-centered base havinga top surface and a bottom surface, wherein said bottom surface is inthermal contact with a heat source; two hollow-centered sidewallslocated on two opposite sides of the base and extending upwardly fromthe top surface of the base; and one or more hollow-centered centercolumns located between the two sidewalls and extending upwardly fromthe top surface of the base, wherein the hollow centers of said base,said sidewalls and said one or more center columns are connected to eachother forming a continuous vapor chamber space, and wherein saidsidewalls and said center columns comprise fins for heat dissipation.

Also disclosed is a heat sink comprising: a planar-shaped first vaporchamber having a first surface and a second surface, wherein said firstsurface is opposite to said second surface and is in contact with a heatsource; a second vapor chamber formed on said second surface, saidsecond vapor chamber is connected to said first vapor chamber thusforming a continuous vapor chamber space; and a plurality ofplanar-shaped heat dissipating fins extending from said second vaporchamber.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings. Tofacilitate this description, like reference numerals designate likestructural elements. Embodiments of the invention are illustrated by wayof example and not by way of limitation in the figures of theaccompanying drawings.

FIG. 1 is a cross-sectional view of a prior art heat sink.

FIGS. 2A and 2B are schematic representations of two embodiments of aheat sink with innovative vapor chamber configuration;

FIG. 3 is a composite of schematic representations of a heat sink withfree-standing center column configuration with (upper panel) or without(lower panel) fins;

FIGS. 4A-4C are results of computational fluid dynamics (CFD) analysisof the heat sink configuration shown in FIG. 3;

FIGS. 5A and 5B are results of CFD analysis of the airflow in the heatsink configuration shown in FIG. 3;

FIG. 6 is a schematic representation of a heat sink with wall-likecenter column configuration;

FIGS. 7A and 7B are results of CFD analysis of the heat sinkconfiguration shown in FIG. 6;

FIGS. 8A and 8B are results of CFD analysis of the airflow in the heatsink configuration shown in FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof wherein like numeralsdesignate like parts throughout, and in which is shown by way ofillustration embodiments in which the invention may be practiced. It isto be understood that other embodiments may be utilized and structuralor logical changes may be made in alternate embodiments. Therefore, thefollowing detailed description is not to be taken in a limiting sense,and the scope of embodiments in accordance with the present invention isdefined by the appended claims and their equivalents.

This description is intended to be read in connection with theaccompanying drawings, which are to be considered pan of the entirewritten description of this invention. The drawing figures are notnecessarily to scale and certain features of the invention may be shownexaggerated in scale or in somewhat schematic form in the interest ofclarity and conciseness, in the description, relative terms such as“horizontal,” “vertical,” “up,” “'down,” “top” and “bottom” as well asderivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,”etc.) should be construed to refer to the orientation as been describedor as shown in the drawing figure under discussion. These relative termsare for convenience of description and normally are not intended torequire a particular orientation. Terms including “inwardly” versus“outwardly,” “upwardly” versus “downwardly,” “longitudinal” versus“lateral” and the like are to be interpreted relative to one another orrelative to an axis of elongation, or an axis or center of rotation, asappropriate. Terms concerning attachments, coupling and the like, suchas “connected” and “interconnected,” refer to a relationship whereinstructures are secured or attached to one another either directly orindirectly through intervening structures, as well as both movable orrigid attachments or relationships, unless expressly describedotherwise. The term “operatively connected” is such an attachment,coupling or connection that allows the pertinent structures to operateas intended by virtue of that relationship.

FIG. 1 is a conceptual illustration of a prior art heat sink with avapor chamber. The vapor chamber is confined in a base plate having alower surface and an upper surface. The lower surface is in thermalcontact with a heat source and the upper surface comprises planar finsextending vertically from the upper surface for heat dissipation.

FIG. 2A illustrates an embodiment of a heat sink with innovative vaporchamber configuration. Heat sink 10 comprises a vapor chamber base 20,vapor chamber sidewalls 30 and optionally one or more vapor chambercenter columns 40. Each of the vapor chamber base 20, vapor chambersidewalls 30 and vapor chamber center columns 40 is a hollow-centeredstructure that comprises a vapor chamber space enclosed by surroundingwalls. In one embodiment, the vapor chamber base 20, the sidewalls 30and the center columns 40 are operatively connected to each other toform a continuous vapor chamber space.

The base 20 contains a bottom surface 22 that is in thermal contact witha heat source, and a top surface 24 on which the sidewalls 30 and/orcenter columns 40 are formed. The base 20 is made of a material having ahigh thermal conductivity, such as a metal or alloy. In one embodiment,the base 20 is made of copper or aluminum. The base 20 is filled orpartially filled with an evaporable working fluid, such as water.

The sidewalls 30 are formed only on selected sides of the base 20 so asto maintain an unobstructed airflow between the sidewalk 30. In theembodiment shown in FIG. 2A, two sidewalk 30 are formed on the oppositesides of the base 20. It should be noted that the sidewalk 30 do notneed to be formed on the edges of the base 20. As shown in FIG. 2B, thetwo sidewalls 30 are formed at locations near the edges of the base 20.

The center column 40 is formed between the sidewalls 30 to furtherfacilitate heat dissipation from the base 20. In one embodiment, thecenter column 40 is in the form of a free-standing column that serves asa heat pipe, Multiple free-standing center columns 40 may be used tofacilitate heat transfer from the base 20 to fins 60. In anotherembodiment, the center column 40 is in the form of a center will that isparallel to the sidewalls 30 and extends from one side of the base 20 tothe other side of the base 20. Multiple center walls may be formedbetween the sidewalk 30 to facilitate heat transfer from the base 20 tofins 60. A person skilled in the art would also understand thatefficient heat dissipation may be achieved with the sidewalls 30 alone,the center columns 40 alone, or a combination of the sidewalk 30 and thecenter columns 40. The sidewalls 30 and center columns 40 are made of amaterial having a high thermal conductivity, such as a metal or alloy.In one embodiment, the sidewalk 30 and center columns 40 made of copperor aluminum.

In one embodiment, the vapor chamber base 20, sidewalls 30 and centercolumns 40 are filled with a porous material 50. The porous material 50has a porosity that allows vapor transport from the base 20, whereevaporation takes place, to sidewalk 30 and center columns 40, wherecondensation of the vapor takes place. The capillary forces created bythe porous material also facilitate the return of condensed workingfluid to the base 20. Examples of the porous material 50 include, butare not limited to, sintered powder wick which can be attached to thevapor chamber base 20, sidewalls 30 and/or center columns 40 by solder.

The sintered powder may be selected from any of the materials havinghigh thermal conductivity and that are suitable for fabrication intoporous structures, e.g., carbon, tungsten, copper, aluminum, magnesium,nickel, gold, silver, aluminum oxide, beryllium oxide, or the like, andmay comprise either substantially spherical, arbitrary or regularpolygonal, or filament-shaped particles of varying cross-sectionalshape. In one embodiment, the porous material 50 comprises sinteredcopper wick. Other wick materials, such as aluminum-silicon-carbide orcopper-silicon-carbide may be used with equal effect.

The sidewalls 30 and/or center columns 40 thriller comprise a pluralityof stacked fins 60 for efficient heat dissipation. The fins 60 areattached in horizontal arrangement to the sidewalls 30 and centercolumns 40. Each fin 60 has a planar-shaped main body having a topsurface 62 and a bottom surface 64 opposite to the top surface 62. Thetop surface 62 of one fin and the bottom surface 64 of the neighboringfin are parallel to each other. The distance (d) between the twoneighboring fins 60 may be determined experimentally to allow forefficient cooling of the fins 60 by airflow. In one embodiment, thedistance (d) is in the range of 0.5-5 mm. The fins 60 are typically madeof a material having high thermal conductivity, such as a metal or analloy. In one embodiment, the fins 60 are made of aluminum.

The heat sink 10 may be used to cool a heat-generating device which maybe an electronic component such as, but not limited to, an integratedcircuit, as memory module, Micro-Electro-Mechanical System (MEMS), asensor, a resister, or a capacitor. The heat sink 10 may be positioneddirectly on the electronic component, or on a thermal solutionincluding, but not limited to, a heat pipe, a heat spreader, a heaterblock, and a thermal transfer plate. A fan may be complementarilypositioned to accelerate airflow between fins 60 and increase the rateof heat dissipation. The exact complementary positioning is applicationdependent, and may be affected by a number of factors, including but notlimited to, the amount of heat to be removed, the volume and velocity ofthe airflow, and so forth. The optimal complementary positioning for aparticular application of flow provider and flow modifier may bedetermined empirically.

During operation, the base 20 of the heat sink 10 absorbs heat generatedby the heat-generating device. The working fluid that is contained inthe inner side of the base 20 absorbs the heat and evaporatessubstantially and moves to the sidewalls 30 and/or center columns 40.Evaporated working fluid is cooled and condensed in the sidewalls 30 andcenter columns 40. The heat is released through fins 60. Finally, thecondensed working fluid flows back to the base 20 to begin anothercycle. In this way, the working fluid can absorb/release amounts ofheat. The heat generated by the heat-generating electronic device isthus transferred from the base 20 to the fins 60 almost immediately.

EXAMPLES Example 1 CFD Analysis of Heat Sink with Free-Standing CenterColumn Configuration

FIGS. 3-5B show results of a CFD analysis of a heat sink withfree-standing center column configuration. As shown in FIG. 3, the heatsink device contains six free-standing center columns 40 that areattached to the vapor chamber base 20. The free-standing center columns40 serve as heat pipes to transfer heat from the base 20 to fins 60.Heat dissipation was achieved by eighteen aluminum plate fins 60attached to the center columns 40. In this embodiment, the fins have athickness of 0.5 mm, a surface area of 80×85 mm, and a fin-to-fin gap of1.1 mm. FIGS. 4A-4C show heat distribution on the center columns 40(FIG. 4A) and fins 60 (FIG. 4B) and the base plate 20 (FIG. 4C). FIGS.5A and 5B show the airflow generated by fins 60.

Example 2

CFD Analysis of Heat Sink with Wall-Like Center Column Configuration

FIGS. 6A-8B show results of a CFD analysis of a heat sink with wall-likecenter column configuration. As shown in FIGS. 6A-6C, the heat sinkdevice contains a base vapor chamber, two sidewalls and a wall-likecenter column. The sidewalls 30 and the center column 40 are operativelyconnected to base 20 and form a continuous vapor chamber space. Heatdissipation was achieved by eighteen aluminum plate fins attached to thecenter columns. The fins have a thickness of 0.5 mm, a surface area of80×85 mm, and a fin-to-fin gap of 1.1 mm. FIGS. 7A-7B show heatdistribution on the base plate 20 (FIG. 7A) and fins 60 (FIG. 7B). FIGS.8A and 8B show the airflow generated by fins 60.

Under the same heat generation and air flow rate settings, the heat sinkwith wall-like center column configuration was able to achieve a 11° C.improvement over the heat sink with five-standing center columnconfiguration, i.e., having a source temperature of 45° C. (FIG. 7B) vs.56° C. (FIG. 4C).

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not limited to thedisclosed embodiments, but, on the contrary, is intended to accommodatevarious modifications and equivalent arrangements. It will beappreciated by those of ordinary skill in the art that a wide variety ofalternate and/or equivalent embodiments or implementations calculated toachieve the same purposes may be substituted for the embodiments shownand described. This application is intended to cover any adaptations orvariations of the embodiments discussed herein. Therefore, it ismanifestly intended that embodiments in accordance with the presentinvention be limited only by the claims and the equivalents thereof.

1. A heat sink comprising: a first vapor chamber section having an uppersurface and a lower surface; a second vapor chamber section extendingvertically fro the upper surface of said first vapor chamber section;and heat-dissipating fins extending horizontally from said second vaporchamber section, wherein said lower surface is in thermal contact with aheat source and wherein said first and second vapor sections areconnected to each other, forming a continuous vapor chamber space. 2.The heat sink of claim 1, wherein said second vapor chamber section isin the form a hollow-centered sidewall.
 3. The heat sink of claim 1,wherein said second vapor chamber section is in the form ahollow-centered center column.
 4. The heat sink of claim 3, wherein saidhollow-centered center column is in the form of a free-standing column.5. The heat sink of claim 3, wherein said hollow-centered center columnis in the form of a center wall.
 6. The heat sink of claim 1, whereinsaid first and second vapor chambers comprise a porous material.
 7. Theheat sink of claim 6, wherein said porous material comprises sinteredpowder wick.
 8. The heat sink of claim 7, wherein said sintered powderwick comprises a material selected from the group consisting of carbon,tungsten, copper, aluminum, magnesium, nickel, gold, silver, aluminumoxide, and beryllium oxide.
 9. The heat sink of claim 8, wherein saidsintered powder wick is sintered copper wick.
 10. The heat sink of claim1, wherein said first and second vapor chambers comprise a material ofhigh thermal conductivity.
 11. The heat sink of claim 10, wherein thematerial of high thermal conductivity comprises copper or aluminum. 12.The heat sink of claim 1, wherein said heat dissipating fins areplanar-shaped and are attached in horizontal arrangement to said secondvapor chamber section.
 13. The heat sink of claim 12, wherein said heatdissipating fins comprises a material of high thermal conductivity, 14.The heat sink of claim 13, wherein the material of high thermalconductivity comprises copper or aluminum.
 15. The heat sink of claim 1,wherein said first vapor chamber section contains a working fluid. 16.The heat sink of claim 15, wherein said working fluid is water.
 17. Aheat sink comprising: a hollow-centered base having a top surface and abottom surface, wherein said bottom surface is in thermal contact with aheat source; two hollow-centered sidewalls located on two opposite sidesof the base and extending upwardly from the top surface of the base; andone or more hollow-centered center columns located between the twosidewalls and extending upwardly from the top surface of the base,wherein the hollow centers of said base, said sidewalls and said one ormore center columns are connected to each other forming a continuousvapor chamber space, and wherein said sidewalls and said center columnscomprise fins for heat dissipation.
 18. The heat sink of claim 16,wherein said fins have a planar shape and extend in directions parallelto said top surface of said hollow-centered base.
 19. A heat sinkcomprising: a planar-shaped first vapor chamber having a first surfaceand a second surface, wherein said first surface is opposite to saidsecond surface and is in contact with a heat source; a second vaporchamber formed on said second surface, said second vapor chamber isconnected to said first vapor chamber thus forming a continuous vaporchamber space; and a plurality of planar-shaped heat dissipating finsextending from said second vapor chamber.
 20. The heat sink of claim 19,wherein said second vapor chamber is a wall-like vapor chamber.